The inventive concept relates to optical communication systems and, more particularly, to multi-channel optical modules capable of transmitting or receiving optical signals of a plurality of wavelengths using one optical fiber.
Recently, Active Optical Cables (AOC) for high-definition multimedia interface (HDMI) and digital visual interface (DVI), which have been increasingly demanded, may need four or more channels capable of concentrating lights of four or more wavelengths in one optical fiber for transmitting audio/video data. However, most marketed AOCs may have structures using a plurality of (e.g., four or two) optical fibers. Thus, it may be difficult to install, maintain, and/or repair the cables of the structures using the plurality of optical fibers. Additionally, a long-distance transmission of the optical signal may be difficult due to the cables of the structures using the plurality of optical fibers.
Generally, a conventional multi-channel optical module capable of concentrating lights of a plurality of wavelengths may have a structure which is optically coupled by reflecting a beam in zigzag-shape using a coarse wavelength division multiplexing (CWDM) filter. In this case, optical path difference between lights of the wavelengths may increase, such that a general condensing lens may not be used and alignment may be very difficult.
Alternatively, according to another conventional art, a multi-channel optical module may include a plurality of light transmitters or light receivers which are aligned in a single metal housing and are fixed by a welder. Here, each of the light transmitters or each of the light receivers may be based on a TO-CAN processing light of one wavelength. However, the optical signal may be reflected or transmitted by an optical filer mounted in the metal housing and then be coupled with one optical fiber. Thus, the optical coupling of the conventional multi-channel optical module may not be easily formed.
The multi-channel optical module described above may include two incline planes of 45 degrees on which filter are mounted. The two incline planes of 45 degrees may have a V-groove. Thus, plane processing may be difficult. Additionally, the filter holder may be formed to have a cylindrical shape, so that the filter holder may be rotated in the metal housing. Thus, the optical path may be tilted. Accordingly, if mismatch may occur by the rotation of the filter holder, optical coupling efficiency of the optical fiber may decrease significantly.
Additionally, in four or more channels, it is difficult to form the filter holder into one body. Thus, two or more filter holders may be used. In this case, the filter holders may be individually mounted, so that mounting positions of the filter holders may be different from each other. Thus, the filter holders may be misaligned with each other. As a result, an incident or transmitted beam may be tilted. The problems may be serious as the number of the channels increases.